The Cisco ASA VPN remote access server must be configured to use AES256 or greater encryption for the IPsec security association to protect the confidentiality of remote access sessions.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-239980 | CASA-VN-000650 | SV-239980r916158_rule | High |
| Description |
| Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, non-organization-controlled network. A block cipher mode is an algorithm that features the use of a symmetric key block cipher algorithm to provide an information service, such as confidentiality or authentication. AES is the FIPS-validated cipher block cryptographic algorithm approved for use in DOD. For an algorithm implementation to be listed on a FIPS 140-2/140-3 cryptographic module validation certificate as an approved security function, the algorithm implementation must meet all the requirements of FIPS 140-2/140-3 and must successfully complete the cryptographic algorithm validation process. Currently, NIST has approved the following confidentiality modes to be used with approved block ciphers in a series of special publications: ECB, CBC, OFB, CFB, CTR, XTS-AES, FF1, FF3, CCM, GCM, KW, KWP, and TKW. |
| STIG | Date |
| Cisco ASA VPN Security Technical Implementation Guide | 2024-08-22 |
Details
| Check Text (C-43213r916141_chk) |
| Verify all IPsec proposals are set to use the AES256 or greater encryption algorithm as shown in the example below. crypto ipsec ikev2 ipsec-proposal IPSEC_TRANS protocol esp encryption aes-256 If the value of the encryption algorithm for any IPsec proposal is not set to use an AES256 or greater algorithm, this is a finding. |
| Fix Text (F-43172r916142_fix) |
| Configure the ASA to use AES256 or greater encryption algorithm to implement IPsec encryption services as shown in the example below. ASA2(config)# crypto ipsec ikev2 ipsec-proposal IPSEC_TRANS ASA2(config-ipsec-proposal)# protocol esp encryption aes-256 ASA2(config-ipsec-proposal)# end |